Transplantation Of Fetal Tissue Research Articles

Evidence of mutant huntingtin and tau-related pathology within neuronal grafts in Huntington’s disease cases

A number of post-mortem studies conducted in transplanted Huntington’s disease (HD) patients from various trials have reported the presence of pathological and misfolded proteins, in particular mutant huntingtin (mHtt) and phosphorylated tau neuropil threads, in the healthy grafted tissue. Here, we extended these observations with histological analysis of post-mortem tissue from three additional HD patients who had received similar striatal allografts from the fetal tissue transplantation trial conducted in Los Angeles in 1998. Immunohistochemical staining was performed using anti-mHtt antibodies, EM48 and MW7, as well as anti-hyperphosphorylated tau antibodies, AT8 and CP13. Immunofluorescence was used to assess the colocalization of EM48+ mHtt aggregates with the neuronal marker MAP2 and/or the extracellular matrix protein phosphacan in both the host and grafts. We confirmed the presence of mHtt aggregates within grafts of all three cases as well as tau neuropil threads in the grafts of two of the three transplanted HD patients. Phosphorylated tau was also variably expressed in the host cerebral cortex of all three subjects. While mHtt inclusions were present within neurons (immunofluorescence co-localization of MAP2 and EM48) as well as within the extracellular matrix of the host (immunofluorescence co-localization of phosphacan and EM48), their localization was limited to the extracellular matrix in the grafted tissue. This study corroborates previous findings that both mHtt and tau pathology can be found in the host and grafts of HD patients years post-grafting.

Research progress of neural stem cells as a source of dopaminergic neurons for cell therapy in Parkinson's disease.

Parkinson's disease (PD) is a neurodegenerative disease, the most characteristic pathological feature is the progressive loss of dopaminergic (DA) neurons in the substantia nigra pars compactus (SNpc) of the mesencephalon, along with reduced dopamine content in the striatum. Researchers have been searching for drugs and therapies to treat PD in decades. However, no approach could stop the progression of the disease, and even some of them caused adverse clinical side effects. PD has a well-defined lesion. Therefore, it is considered to be one of the most curable central nervous system diseases by cell replacement treatment. Fetal ventral mesencephalic tissue transplantation has been used to treat patients with PD and obtained positive treatment results. However, ethical issues, such as limited donor tissue, and side effects including graft-induced dyskinesias, limit its clinical applications. Neural stem cell (NSC) transplantation is a viable therapy choice because it possesses multipotency, self-renewal ability, and differentiation into DA neurons, which may substitute for lost DA neurons and slow down the neurodegenerative process in PD. Studies that investigated the delivery of NSCs by using animal models of PD revealed survival, migration, and even amelioration of behavioral deficits. Here, the research progress of NSCs or NSC-derived DA neurons in treating PD was reviewed, and the practicability of present manufacturing processes for clinical testing was considered. This review is expected to offer ideas for practical strategies to solve the present technical and biological problems related to the clinical application of NSCs in PD.

Gestación ovárica ectópica y subunidad β de gonadotropina coriónica negativa ¿es posible? Reporte de un caso infrecuente

Ovarian ectopic gestation occurs when fetal tissue implants outside the uterine cavity. Implantation is usually tubal; Ovarian localization has an incidence of less than 1%. The diagnosis is confirmed by ultrasonography and the β subunit of chorionic gonadotropin in urine or blood; But its negativity doesn’t rule out the diagnosis. We present the case of a 19-year-old nulliparous patient with pelvic pain, with no significant history. Ultrasound revealed a 65 mm right ovary tumor. The β subunit value of chorionic gonadotropin was 3 mIU/L. The operative findings were: 100 cc hemoperitoneum, ruptured right ovary cyst of 6 x 4 cm ruptured, ectopic pregnancy of 7 weeks of gestation in Douglas sac fundus and phlegmonous appendix. The anatomopathological study reflected: moderate periappendicitis, right ovary with inflammation, neovascularization, vascular congestion, recent hemorrhage and ovarian ectopic pregnancy

Morphological and molecular expression patterns of neural precursor cells derived from human fetal spinal cord in two-, three-dimensional, and organoid culture environments

Recently, interest in three-dimensional (3D) cell or tissue organoids that may, in vitro, overcome not only the practical problems associated with fetal tissue transplantation, but also provide a potential source for the regeneration of injured spinal cords, has been increasing steadily. In this study, we showed that human neural precursor cells (hNPCs) derived from the fetal spinal cord could be incubated in serum free medium at two dimensional (2D), three dimensional (3D) and tissue organoid-systems. Additionally, we investigated morphological changes over time along with the expression of proteoglycans, collagen, or myelin in 2D, 3D and tissue-like organoids. 2D cells exhibited a spindle-shaped morphology with classic hill and valley growth patterns, while 3D cells grew as clusters of undifferentiated cells and cell sheets (tissue organoids) that gradually rolled up like a carpet without forming a circular cell mass. Immunostaining was performed to demonstrate the expression of TUJ-1, MAP-2, GAD 65/67 and ChAT in 2D cells or tissue-like organoids, which stained positively for them. In addition, we observed the immunoreactivity of HNu, NG2, TUJ-1, and GFAP in tissue-like organoids. The organoid culture system studied in our work may be used as therapeutic agents for spinal cord injury (SCI), and as raw materials needed for development of new medicines to improve human responses and cure diseases.

Combined cell-based therapy strategies for the treatment of Parkinson's disease: focus on mesenchymal stromal cells.

Parkinson's disease is a neurodegenerative condition characterized by motor impairments caused by the selective loss of dopaminergic neurons in the substantia nigra. Levodopa is an effective and well-tolerated dopamine replacement agent. However, levodopa provides only symptomatic improvements, without affecting the underlying pathology, and is associated with side effects after long-term use. Cell-based replacement is a promising strategy that offers the possibility to replace lost neurons in Parkinson's disease treatment. Clinical studies of transplantation of human fetal ventral mesencephalic tissue have provided evidence that the grafted dopaminergic neurons can reinnervate the striatum, release dopamine, integrate into the host neural circuits, and improve motor functions. One of the limiting factors for cell therapy in Parkinson's disease is the low survival rate of grafted dopaminergic cells. Different factors could cause cell death of dopaminergic neurons after grafting such as mechanical trauma, growth factor deprivation, hypoxia, and neuroinflammation. Neurotrophic factors play an essential role in the survival of grafted cells. However, direct, timely, and controllable delivery of neurotrophic factors into the brain faces important limitations. Different types of cells secrete neurotrophic factors constitutively and co-transplantation of these cells with dopaminergic neurons represents a feasible strategy to increase neuronal survival. In this review, we provide a general overview of the pioneering studies on cell transplantation developed in patients and animal models of Parkinson's disease, with a focus on neurotrophic factor-secreting cells, with a particular interest in mesenchymal stromal cells; that co-implanted with dopaminergic neurons would serve as a strategy to increase cell survival and improve graft outcomes.

Behavioral context improves optogenetic stimulation of transplanted dopaminergic cells in unilateral 6-OHDA rats

Stem cell therapy has long been a popular method of treatment for Parkinson’s disease currently being researched in both preclinical and clinical settings. While early clinical results are based upon fetal tissue transplants rather than stem cell transplants, the lack of successful integration in some patients and gradual loss of effect in others suggests a more robust protocol is needed. We propose a two-front approach, one where transplants are directly stimulated in coordination with host activity elicited by behavioral tasks, which we refer to as behavioral context. After a pilot with unilateral 6-OHDA rats transplanted with dopaminergic cells differentiated from mesenchymal stem cells that were optogenetically stimulated during a swim task, we discovered that early stimulation predicted lasting reduction of motor deficits, even in the absence of later stimulation. This led to a follow-up with n = 21 rats split into three groups: one stimulated while performing a swim task (Stim-Swim; St-Sw), one not stimulated while swimming (NoStim-Swim; NSt-Sw), and one stimulated while stationary in a bowl (Stim-NoSwim; St-NSw). After initial stimulation (or lack thereof), all rats were retested two and seven days later with the swim task in the absence of stimulation. The St-Sw group gradually achieved and maintained symmetrical limb use, whereas the NSt-Sw group showed persistent asymmetry and the St-NSw group showed mixed results. This supports the notion that stem cell therapy should integrate targeted stimulation of the transplant with behavioral stimulation of the host tissue to encourage proper functional integration of the graft.

Subretinal Transplantation of Human Embryonic Stem Cell-Derived Retinal Tissue in a Feline Large Animal Model.

Retinal degenerative (RD) conditions associated with photoreceptor loss such as age-related macular degeneration (AMD), retinitis pigmentosa (RP) and Leber Congenital Amaurosis (LCA) cause progressive and debilitating vision loss. There is an unmet need for therapies that can restore vision once photoreceptors have been lost. Transplantation of human pluripotent stem cell (hPSC)-derived retinal tissue (organoids) into the subretinal space of an eye with advanced RD brings retinal tissue sheets with thousands of healthy mutation-free photoreceptors and has a potential to treat most/all blinding diseases associated with photoreceptor degeneration with one approved protocol. Transplantation of fetal retinal tissue into the subretinal space of animal models and people with advanced RD has been developed successfully but cannot be used as a routine therapy due to ethical concerns and limited tissue supply. Large eye inherited retinal degeneration (IRD) animal models are valuable for developing vision restoration therapies utilizing advanced surgical approaches to transplant retinal cells/tissue into the subretinal space. The similarities in globe size, and photoreceptor distribution (e.g., presence of macula-like region area centralis) and availability of IRD models closely recapitulating human IRD would facilitate rapid translation of a promising therapy to the clinic. Presented here is a surgical technique of transplanting hPSC-derived retinal tissue into the subretinal space of a large animal model allowing assessment of this promising approach in animal models.

Persistent dyskinesias in patients with fetal tissue transplantation for Parkinson disease

Cell transplants are being developed for patients with Parkinson disease (PD) who have insufficient benefit with standard medical treatment. We describe the clinical features of five patients who developed persistent dyskinesias after fetal dopaminergic tissue transplantation. All had levodopa-induced dyskinesias preoperatively. We implanted fetal mesencephalic dopaminergic tissue into the putamina bilaterally in 34 patients with advanced PD. They were not immunosuppressed. Five of 34 patients (15%) developed troublesome choreic or dystonic dyskinesias that persisted despite lowering or discontinuing medications. Attempts to treat the involuntary movements with amantadine, clozapine, anticholinergics, dopamine depletors and other medicines had limited success. Metyrosine eliminated dyskinesias but led to the parkinsonian “off” state. Increasing the dose of levodopa worsened the dyskinesias. Three patients required placement of pallidal stimulators, bilaterally in two and unilaterally in one patient who had only contralateral dyskinesias. The two with the bilateral stimulators had improvement in dyskinesias. The patient with the unilateral pallidal stimulator had a substantial reduction of the dyskinesias, but attempts to treat residual “off” symptoms with levodopa were limited by worsening dyskinesias. Although the number of patients developing these persistent dyskinesias was small, these five patients had dramatic improvement after transplant. As a group, they had milder Parkinson signs at baseline and improved to the point of having minimal parkinsonism, with reduction or elimination of levodopa therapy prior to developing persistent dyskinesias. These involuntary movements establish the principle that fetal dopaminergic tissue transplants can mimic the effects of levodopa, not only in reducing bradykinesia, but also in provoking dyskinesias.

Revisiting cell and gene therapies in Huntington's disease.

Neurodegenerative movement disorders, such as Huntington's disease (HD), share a progressive and relentless course with increasing motor disability, linked with neuropsychiatric impairment. These diseases exhibit diverse pathophysiological processes and are a topic of intense experimental and clinical research due to the lack of therapeutic options. Restorative therapies are promising approaches with the potential to restore brain circuits. However, there were less compelling results in the few clinical trials. In this review, we discuss cell replacement therapies applied to animal models and HD patients. We thoroughly describe the initial trials using fetal neural tissue transplantation and recent approaches based on alternative cell sources tested in several animal models. Stem cells were shown to generate the desired neuron phenotype and/or provide growth factors to the degenerating host cells. Besides, genetic approaches such as RNA interference and the CRISPR/Cas9 system have been studied in animal models and human-derived cells. New genetic manipulations have revealed the capability to control or counteract the effect of human gene mutations as described by the use of antisense oligonucleotides in a clinical trial. In HD, innovative strategies are at forefront of human testing and thus other brain genetic diseases may follow similar therapeutic strategies.

Autologous transplant therapy alleviates motor and depressive behaviors in parkinsonian monkeys.

Degeneration of dopamine (DA) neurons in the midbrain underlies the pathogenesis of Parkinson's disease (PD). Supplement of DA via L-DOPA alleviates motor symptoms but does not prevent the progressive loss of DA neurons. A large body of experimental studies, including those in nonhuman primates, demonstrates that transplantation of fetal mesencephalic tissues improves motor symptoms in animals, which culminated in open-label and double-blinded clinical trials of fetal tissue transplantation for PD1. Unfortunately, the outcomes are mixed, primarily due to the undefined and unstandardized donor tissues1,2. Generation of induced pluripotent stem cells enables standardized and autologous transplantation therapy for PD. However, its efficacy, especially in primates, remains unclear. Here we show that over a 2-year period without immunosuppression, PD monkeys receiving autologous, but not allogenic, transplantation exhibited recovery from motor and depressive signs. These behavioral improvements were accompanied by robust grafts with extensive DA neuron axon growth as well as strong DA activity in positron emission tomography (PET). Mathematical modeling reveals correlations between the number of surviving DA neurons with PET signal intensity and behavior recovery regardless autologous or allogeneic transplant, suggesting a predictive power of PET and motor behaviors for surviving DA neuron number.

Gene Therapy in the Management of Parkinson's Disease: Potential of GDNF as a Promising Therapeutic Strategy.

The limitations of conventional treatment therapies in Parkinson's disorder, a common neurodegenerative disorder, lead to the development of an alternative gene therapy approach. Multiple treatment options targeting dopaminergic neuronal regeneration, production of enzymes linked with dopamine synthesis, subthalamic nucleus neurons, regulation of astrocytes and microglial cells and potentiating neurotrophic factors, were established. Viral vector-based dopamine delivery, prodrug approaches, fetal ventral mesencephalon tissue transplantation and dopamine synthesizing enzyme encoding gene delivery are significant therapies evidently supported by numerous trials. The review primarily elaborates on the significant role of glial cell-line derived neurotrophic factor in alleviating motor symptoms and the loss of dopaminergic neurons in Parkinson's disease. Neuroprotective and neuroregenerative effects of GDNF were established via preclinical and clinical study outcomes. The binding of GDNF family ligands with associated receptors leads to the formation of a receptor-ligand complex activating Ret receptor of tyrosine kinase family, which is only expressed in dopaminergic neurons, playing an important role in Parkinson's disease, via its association with the essential protein encoded genes. Furthermore, the review establishes delivery aspects, like ventricular delivery of recombinant GDNF, intraparenchymal and intraputaminal delivery using infusion catheters. The review highlights problems and challenges of GDNF delivery, and essential measures to overcome them, like gene therapy combinations, optimization of delivery vectors, newer targeting devices, motor symptoms curbing focused ultrasound techniques, modifications in patient selection criteria and development of novel delivery strategies based on liposomes and encapsulated cells, to promote safe and effective delivery of neurotrophic factor and establishment of routine treatment therapy for patients.

Transplantation of fetal liver tissue coated by ultra-purified alginate gel over liver improves hepatic function in the cirrhosis rat model

In this study, we used a new coating agent, that is, ultra-purified alginate gel (UPAL), for fetal liver tissue transplantation. This study aims to compare the effect of UPAL with the effect of other coating agents on improving the effect of fetal liver tissue transplantation in a liver cirrhosis rat model. Prior to the transplantation of wild-type ED14 fetal liver tissues, various coating agents were separately applied on the liver surface of rats with cirrhosis. Then, we compared the engraftment area, engraftment rate and liver function level of these rats. As a result, coating the liver surface of a cirrhosis rat with UPAL obtained the best effect in terms of engraftment area and engraftment rate of the transplanted liver tissue and in the recovery of liver function compared with control group. Therefore, UPAL coating may serve as a novel strategy for liver organoid transplantation.

Co-transplantation of Vascularized Thymic Graft with Kidney in Pig-to-Nonhuman Primates for the Induction of Tolerance Across Xenogeneic Barriers.

Using advanced gene editing technologies, xenotransplantation from multi-transgenic alpha-1,3-galactosyltransferase knockout pigs has demonstrated marked prolongation of renal xenograft survival, ranging from days to greater than several months for life-supporting kidneys and >2years in a heterotopic non-life-supporting cardiac xenograft model. However, continuous administration of multiple immunosuppressive drugs continues to be required, and attempts to taper immunosuppression have been unsuccessful. These data are consistent with previous reports indicating that the human-anti-porcine T cell response is similar or stronger than that across allogeneic barriers. Due to the strength of both the innate and adaptive immune responses in xenotransplantation, the level of continuous immunosuppression needed to control these responses and prolong xenograft survival has been associated with prohibitive morbidity and mortality. These facts provide compelling rationale to pursue a clinically applicable strategy for the induction of tolerance.Mixed chimerism and thymic tissue transplantation have both achieved xenogeneic tolerance in pig-to-mouse models, and both have recently been extended to pig-to-baboon models. Although these strategies are promising in small animal models, neither direct intravenous injection of porcine bone marrow cells nor direct fetal thymic tissue transplantation into recipients was able to achieve >2days chimerism following BM Tx or the engraftment of thymic tissues across xenogeneic barriers in pig-to-nonhuman primate models. Several innovative procedures have been largely developed by Kazuhiko Yamada to overcome these failures. These include vascularized thymic transplantation, combined with either thymokidney (TK) or vascularized thymic lobe (VTL) transplantation. Utilizing the strategy of transplanting vascularized thymic grafts with kidney from the same GalT-KO donor without further gene modification, we have achieved longer than 6 months survival of life-supporting kidneys in a baboon. Notably, the recipient became donor specific unresponsive and developed new thymic emigrants. In this chapter, we introduce a brief summary of our achievements to date toward the successful induction of tolerance by utilizing our novel strategy of vascularized thymic transplantation (including thymokidney transplantation), as well as describe the step-by-step methodology of surgical and in vitro procedures which are required for this experiment.

Improvement of Spatial Learning and Memory Impairments by Fetal Neural Tissue Transplantation in Experimental Rat Model of Alzheimer’s Disease

ABSTRACT Objective: It is known that the acetylcholinergic afferents of the neocortex from subcortical areas participate in learning and memory. Autopsy studies in cases of Alzheimer’s disease have shown that most of the neurons of nucleus basalis magnocellularis are atrophic or decreased in number. In this study, we searched for whether or not it was possible to improve the impaired learning and memory functions with fetal neural tissue transplantation in an experimental model of Alzheimer ‘s disease. Material & Methods: A total of thirty seven young adult male Wistar albino rats were served as experimental subjects.The nucleus basalis magnocellularis on the right side was destroyed by the injection of kainic acid stereotactically so as to make a model of Alzheimer’s disease. The grafts were obtained from 14-16 day old fetuses of the same genus.After the tissue with cholinergic neurons dissected from ventral forebrain and tissue with non-cholinergic neurons dissected from telencephalic vesicle, cell suspensions were prepared and injected stereotactically to the ipsilateral frontal cortex. Spatial learnig and memory functions were tested by Morris’ water maze tasks. Results: Spatial learning and memory functions in rats were impaired by unilateral lesions of nucleus basalis magnocellularis. The impairment observed during the early period partially improved by the time. It was observed that this amelioration was accelerated with both cholinergic and non-cholinergic fetal neural tissue implantation Conclusion: In our study, improvement of spatial learning and memory impairment with both cholinergic and non-cholinergicfetal neural tissue implantation can be explained by reestablishment of impaired connections via proliferation of limited number of surviving cholinergic neurons creating new synapses, as a result of upregulation of endogenous neural stem cells and activation of trophic mechanisms by implantation, rather than creation of functional synapses between the graft andthe recipient tissue.

Designing stem-cell-based dopamine cell replacement trials for Parkinson's disease.

Clinical studies of Parkinson's disease (PD) using a dopamine cell replacment strategy have been tried for more than 30 years. The outcomes following transplantation of human fetal ventral mesencephalic tissue (hfVM) have been variable, with some patients coming off their anti-PD treatment for many years and others not responding and/or developing significant side effects, including graft-induced dyskinesia. This led to a re-appraisal of the best way to do such trials, which resulted in a new European-Union-funded allograft trial with fetal dopamine cells across several centers in Europe. This new trial, TRANSEURO ( NCT01898390 ), is an open-label study in which some individuals in a large observational cohort of patients with mild PD who were undergoing identical assessments were randomly selected to receive transplants of hfVM. The TRANSEURO trial is currently ongoing as researchers have completed both recruitment into a large multicenter observational study of younger onset early-stage PD and transplantation of hfVM in 11 patients. While completion of TRANSEURO is not expected until 2021, we feel that sharing the rationale for the design of TRANSEURO, along with the lessons we have learned along the way, can help inform researchers and facilitate planning of transplants of dopamine-producing cells derived from human pluripotent stem cells for future clinical trials.

Gestational Age-Dependent Fetal Fluid Dynamics in the Ovine Developmental Model: Establishment of Surrogate Markers for the Differentiation of Stem Cell Origin

The ovine developmental model represents the standard in vivo model for studies involving maternofetal physiology, amniotic fluid (AF) research, and fetal cell therapy prior to human clinical use. Although being close to the human fetal anatomy, 2 separate extraembryonic fluid compartments remain during gestation, known as the amnion and the allantois. A clear distinction between AF versus allantoic fluid (AL) is therefore indispensable for correct scientific conclusions with regard to human translation. In the presented study, the biochemical composition of AF and AL was evaluated in ovine gravid uteri postmortem (n = 31) over the entire gestation. Four parameters, consisting of Na⁺, Cl^–, Mg²⁺, and total protein, have been found to allow for specific discrimination of the 2 fetal fluids at all gestational phases and therefore as potential surrogate parameters for gestational age. In addition, volumetric changes of the developing fetus and the 2 fetal fluid cavities were analyzed by contrast-enhanced computed tomography (n = 12). AF showed a significant, linear volumetric increase over gestation, whereas AL volume maintained relatively static independent of gestational age. These results serve as a basis for future studies by providing surrogate markers enabling a reliable distinction of isolated fetal fluids and contained cells in the ovine developmental model over the entire gestation.

In Honor of LeRoy Walters: Introduction from the Editors.

In Honor of LeRoy Walters: Introduction from the Editors Eric M. Meslin (bio), Eric T. Juengst (bio), and Carol Mason Spicer (bio) Since the birth of bioethics, a persistent refrain has been that advances in science, technology, and health are occurring so quickly that they threaten to outpace society’s ability to understand and react to them. Genomics, big data, and synthetic biology preoccupy current scholarly and policy debates, just as organ transplantation, in vitro fertilization, human subjects research, and gene therapy did over the past forty years. But the history of bioethics is more than the topics it has addressed. It is also the story of the people whose voices shaped its debates and built society’s capacity to manage the escalating pace of technological change. LeRoy Walters is one of those contributors who made a difference. He is part of an original community of scholars and intellectuals who were involved in these issues from the earliest days of bioethics. Now an Emeritus Faculty at the Kennedy Institute of Ethics at Georgetown University, Walters joined the Kennedy Institute in 1971 as its first faculty member appointed to a multi-year term by the new Director, Andre Hellegers, and has remained affiliated with the Institute ever since. His academic training at Messiah College, Associated Mennonite Seminaries, University of Heidelberg, Free University of Berlin, and Yale University focused on religious studies culminating in a Ph.D. on just war theory that provided the moral foundation for his ongoing work. Rising through the academic ranks until becoming the Joseph P. Kennedy, Sr., Professor of Christian Ethics in 1993, Walters was also Director of the Kennedy Institute for a three-year period. In addition to teaching and mentoring during his tenure at the Institute, he was also a bioethics “builder.” He envisioned and implemented Bioethicsline, one of the first online, annotated databases for bioethics research in the world. Linked to the National Library of Medicine, Bioethicsline served as a portal to what would become the National Reference Center for Bioethics Literature, the largest resource of its kind in the world. During his tenure, the Kennedy Institute began housing the collections of past [End Page xi] bioethics commissions and advisory bodies and an innovative DNA Patent Database, an unusual project for a bioethicist. Walters was a recently appointed Associate Professor when the editors and contributors to this special issue of KIEJ first encountered him as graduate students and colleagues in the early 1980s. Generations of students and colleagues have subsequently benefitted from his wisdom and gracious mentoring, but so too have countless federal agencies, departments, advisory committees, and working groups that he assisted as a consultant, member, or chair. Walters was involved in many of the most significant bioethics policy discussions occurring in the U.S. from the 1970s through the 2000s. He was a consultant to the National Institute of Child Health and Human Development, the DHEW Ethics Advisory Board, and the National Commission for the Protection of Human Subjects of Biomedical and Behavioral Research, for whom he prepared a key background paper on fetal research and participated in the development of its Belmont Report. He served for three terms on the NIH Recombinant DNA Advisory Committee, chairing the committee’s Working Group on Human Gene Therapy, which established review criteria for clinical gene transfer research and is still functioning four decades later. He chaired the NIH Human Fetal Tissue Transplantation Research Panel; sat on the Ethical, Legal and Social Implications Research Planning and Evaluation Group Program of the National Human Genome Research Institute; was a member of the Bioethics Committee of the National March of Dimes, the DHEW Secretary’s Task Force on Compensation of Injured Research Subjects, and as a committee member of Institute of Medicine studies on AIDS and vaccine development. He was an influential advisor and consultant to the Congressional Office of Technology Assessment, Office for Protection from Research Risks, and two presidential bioethics commissions. In addition to his policy influence, he is a prolific writer and aggregator of resources for use by others. Walters is responsible for creating and co-editing with Tamar Joy Kahn and Doris Mueller Goldstein thirty-five volumes of the Bibliography of Bioethics...

Repairing the Brain: Cell Replacement Using Stem Cell-Based Technologies.

Current approaches to cell replacement therapy in Parkinson’s disease are strongly focused on the dopamine system, with the view that restoring dopaminergic inputs in a localized and physiologic manner will provide superior benefits in terms of effect and longevity compared with oral medication. Experience using transplants of fetal tissue containing dopaminergic cell precursors has provided valuable proof that the approach is feasible, and that engrafted cells can survive and function over many years. However, multiple drawbacks and procedural complications are recognized in using fetal cells. Recent strides in stem cell technology now make it possible to overcome some of the barriers associated with fetal tissue. In particular the generation of high numbers of specific cell types, such as dopaminergic neurons, from stem cells means that quality, consistency, activity, and safety can be more thoroughly determined prior to transplantation, thus providing hope for more robust outcomes. These cells are also predicted to provide benefit without leading to the graft-induced dyskinesia that led to morbidity in a subset of individuals who underwent fetal mesencephalic cell and tissue grafting in the 1990s. In thinking about developing such novel therapeutics, the choice of starting material has also expanded, with the availability of multiple human embryonic stem cell lines, as well as the possibilities for producing induced pluripotent cells, or neuronal cells from a patient’s own tissue. In this article, we speculate on how rapidly expanding knowledge and technical possibilities may impact on stem cell-based therapies for cell replacement in Parkinson’s disease over the next two decades.

Astrogliosis has Different Dynamics after Cell Transplantation and Mechanical Impact in the Rodent Model of Parkinson's Disease.

Background:Transplantation of fetal mesencephalic tissue is a well-established concept for functional reinnervation of the dopamine-depleted rat striatum. However, there is no extensive description of the glial response of the host brain following this procedure.Aims:The present study aimed to quantitatively and qualitatively analyse astrogliosis surrounding intrastriatal grafts and compare it to the reaction to mechanical injury with the transplantation instrument only.Study Design:Animal experimentation.Methods:The standard 6-hydroxydopamine-induced unilateral model of Parkinson’s disease was used. The experimental animals received transplantation of a single-cell suspension of E14 ventral mesencephalic tissue. Control animals (sham-transplanted) were subjected to injury by the transplantation cannula, without injection of a cell suspension. Histological analyses were carried out 7 and 28 days following the procedure by immunohistochemistry assays for tyrosine hydroxylase and glial fibrillary acidic protein. To evaluate astrogliosis, the cell density and immunopositive area were measured in distinct zones within and surrounding the grafts or the cannula tract.Results:Statistical analysis revealed that astrogliosis in the grafted striatum increased from day 7 to day 28, as shown by a significant change in both cell density and the immunopositive area. The cell density increased from 816.7±370.6 to 1403±272.1 cells/mm2 (p<0.0001) аnd from 523±245.9 to 1164±304.8 cells/mm2 (p<0.0001) in the two zones in the graft core, and from 1151±218.6 to 1485±210.6 cells/mm2 (p<0.05) for the zone in the striatum immediately adjacent to the graft. The glial fibrillary acidic protein-expressing area increased from 0.3109±0.1843 to 0.7949±0.1910 (p<0.0001) and from 0.1449±0.1240 to 0.702±0.2558 (p<0.0001) for the same zones in the graft core, and from 0.5277±0.1502 to 0.6969±0.1223 (p<0.0001) for the same area adjacent to the graft zone. However, astrogliosis caused by mechanical impact only (control) did not display such dynamics. This finding suggests an influence of the grafted cells on the host’s glia, possibly through cross-talk between astrocytes and transplanted neurons.Conclusion:This bidirectional relationship is affected by multiple factors beyond the mechanical trauma. Elucidation of these factors might help achieve better functional outcomes after intracerebral transplantation.

Fetal Chimerism and Fetal Thymic Transplantation

Fetal tissue transplantation is an attractive field of modern medicine that can have immense application in treating several refractile conditions. Fetal tissue transplantation is an allogeneic transplantation procedure and like any allogeneic transplantation they contribute towards the formation of a chimera at the cellular and tissue level grossly and can be classified as a macro chimerism. The fetus during the time of pregnancy also takes part in microchimerism through fetomaternal cell trafficking where there is an exchange of the maternal and the fetal cells through the blood-placental barrier. Apart from the creation of a stable chimerism, fetal tissues also play a role in healing. Fetal thymic transplantation is one of the most exciting applications of regenerative medicine which has also been discussed briefly with some case studies.